Conventional Wisdom: more lanes are better

economicdisconnect.blogspot.com

On my way to work this morning I heard Mayor Villaraigosa of LA make the following statement on NPR's Morning Edition the Marketplace Morning Report:

"That HOV lane that we will build will relieve the most congested freeway in the United States."

He of course, was talking about the major expansion project on the 405 freeway and the resulting Carmageddon. But I was struck by how such a bold statement could go unquestioned. I didn't think it was accurate so I dug into the interwebs until I found this:

[in 1989] the Southern California Association of Governments concluded that traffic-assistance measures, be they adding lanes, or even double-decking the roadways, would have no more than a cosmetic effect on Los Angeles' traffic problems. 

Why you ask? Because according to economists Gilles Duranton and Matthew Turner, vehicle miles traveled increases essentially one-to-one with the number of miles of new highway. They call this phenomenon the fundamental law of road congestion(via Triumph of the City by Ed Glaeser, p). And it has been well documented.

In the Mayor's defense he also talked about the desire to improve LA's mass transit which, in theory, would help the congestion problem:

Even allowing that a train track could be wider than a highway lane, one train line could replace an entire highway, even a highway with five lanes in each direction (such as L.A.’s Interstate 405).